With the availability of labeled homocarnosine, carnosine, and histidine, the metabolism of the dipeptides will be studied in brain. This includes their synthesis as well as their breakdown. Specific brain areas as well as specific cellular and intracellular locations will be investigated. The possible alteration in metabolism in diseased states of brain will be investigated using animals as model systems. With the availability of pure homocarnosine-carnosine synthetase, a localization of the enzyme in brain using immunohistochemical techniques will be attempted. BIBLIOGRAPHIC REFERENCES: "Distribution of Homocarnosine-Carnosine Synthetase in Tissues of Rat, Mouse, Chick and Frog", Ng, R.H. and Marshall, F.D., Comp. Biochem. Physiol., 1976, (in press). "Subcellular Distribution and Some Properties of Homocarnosine-Carnosine Synthetase from Chick Red Blood Cells", Ng, R.H. and Marshall, F.D., Comp. Biochem. Physiol., 1976 (in press).